Arts ACT is planning to repair damaged public art works in the city centre after a drop in vandalism.

One of the sculptures which shows four small men reading books while climbing a staircase has been left in a state of disrepair for about two years.

A vandal tore off one of the bronze figures, which was replaced then weeks later, then two people used a hacksaw to remove the new one.

A third was also ripped from the sculpture.

Arts ACT director David Whitney says his department tried to fix it shortly after one of the men was stolen, but it was damaged again within days.

"We got a replacement little man to put in there and even though we attached particular steel rods to the base of the feet and we filled the body of the staircase up with concrete, two people arrived with a hacksaw and we've got CCTV footage of them with a hacksaw deliberately taking a trophy," Mr Whitney said.

Arts ACT says security is an issue for prominent artworks across the city.

"One of the things that obviously concerns us, is do we want to go though the process of replacing that art work and then having it stolen again," he said.

"It did take some time for the artist to remake the two men that we had to get replaced and so they've now arrived in Canberra and are here."

The directorate recently had to replace the glass sphere in the ACT Memorial on London Circuit with a granite ball, after panels in the original work were smashed.

A large granite loop on Northbourne Avenue has also been repaired after it was tagged by vandals using spray paint.